Effects of a mixture of monopropionine and monobutyrin on the fermentation quality and aerobic stability of whole crop maize silage

The ensiling of high DM content maize, with the aim of achieving a higher proportion of starch in the silage, leads to difficulties in containing aerobic spoilage, due to its low lactic acid bacteria (LAB) activity during fermentation. The aim of the present study has been to evaluate the effects of a new chemical additive, containing a mixture of monopropionine and monobutyrin, on the aerobic stability of whole crop maize silages in two trials in which the conservation period differed. Maize was harvested at a DM of around 410 g/kg and was then untreated (C) or treated with L. buchneri (LB) NCIMB 40788, a new additive, which was applied at a rate of 5 g/kg fresh matter (FM) (A0.5), at rate of 10 g/kg FM (A1.0) and at rate of 15 g/kg FM (A1.5). The obtained silages were conserved for 100 d and 240 d for Trials I and II, respectively. At opening, the DM losses, chemical composition, fermentation profile, microbial counts and aerobic stability were determined for each silo. In both trials, the addition of the chemical additive influenced the fermentation profile, and a lower level of acetic acid and ethanol was observed than for the C and LB silages. The propionic and butyric acids were only found in the silages treated with the chemical additive at concentrations that were linearly related to the calculated amount derived from the acid hydrolysis of the additive, thus indicating no clostridia activity had occurred. The application of the new additive reduced the yeast count, and aerobic stability was thus improved. The aerobic stability increased in an added dose dependent manner, with a mean increase of 120 h in A1.5, compared to the C silages. The DM losses were higher in the C silages than in the A1.5 ones. The chemical additive did not affect the nutritional parameters. The addition of LB was not very efficient, probably due to the low water activity of the maize with high DM content and the low temperature at harvesting, which could have negatively influenced its activity. The addition of monopropionine and monobutyrin showed a positive effect, as it improved the aerobic stability, even in less than optimal conditions (high DM maize content and low temperature). The effect of the additive was related to its application rate, with the best results being observed when it was applied at 1.5% of fresh matter.